ICS85354AK ICST [Integrated Circuit Systems], ICS85354AK Datasheet - Page 12

• Manufacturer Part Number: ICS85354AK
• Description: DUAL 2:1/1:2 DIFFERENTIAL -TO-LVPECL/ECL MULTIPLEXER
• Manufacturer: ICST [Integrated Circuit Systems]

This section provides information on power dissipation and junction temperature for the ICS85354.
Equations and example calculations are also provided.
1. Power Dissipation.
The total power dissipation for the ICS85354 is the sum of the core power plus the power dissipated in the load(s).
The following is the power dissipation for V
NOTE: Please refer to Section 3 for details on calculating power dissipated in the load.
2. Junction Temperature.
Junction temperature, Tj, is the temperature at the junction of the bond wire and bond pad and directly affects the reliability of the
device. The maximum recommended junction temperature for HiPerClockS
In order to calculate junction temperature, the appropriate junction-to-ambient thermal resistance θ
moderate air flow of 0 linear feet per minute and a multi-layer board, the appropriate value is 51.5°C/W per Table 6 below.
Therefore, Tj for an ambient temperature of 85°C with all outputs switching is:
This calculation is only an example. Tj will obviously vary depending on the number of loaded outputs, supply voltage, air flow,
and the type of board (single layer or multi-layer).
T
85354AK
ABLE
•
•
The equation for Tj is as follows: Tj = θ
Tj = Junction Temperature
θ
Pd_total = Total Device Power Dissipation (example calculation is in section 1 above)
T
85°C + 0.243W * 51.5°C/W = 97.5°C. This is well below the limit of 125°C.
JA
A
Multi-Layer PCB, JEDEC Standard Test Boards
= Ambient Temperature
6. T
= Junction-to-Ambient Thermal Resistance
Power (core)
Power (outputs)
If all outputs are loaded, the total power is 4 * 27.83mW = 111.3mW
Total Power
HERMAL
Integrated
Circuit
Systems, Inc.
R
MAX
ESISTANCE
_MAX
MAX
= V
= 27.83mW/Loaded Output pair
(3.465, with all outputs switching) = 131.7mW + 111.3mW = 243mW
CC_MAX
θ θ θ θ θ
* I
JA
EE_MAX
FOR
θ θ θ θ θ
JA
P
CC
16-
= 3.465V * 38mA = 131.7mW
JA
by Velocity (Linear Feet per Minute)
= 3.465V, which gives worst case results.
www.icst.com/products/hiperclocks.html
* Pd_total + T
OWER
PRELIMINARY
PIN
VFQFN, F
C
A
ONSIDERATIONS
D
ORCED
12
IFFERENTIAL
51.5°C/W
C
0
ONVECTION
TM
devices is 125°C.
-
TO
-LVPECL/ECL M
JA
must be used. Assuming a
ICS85354
D
UAL
REV. B JUNE 8, 2004
ULTIPLEXER
2:1/1:2